Methods and systems for transforming luminal images

ABSTRACT

The invention provides methods and systems for correcting translational distortion in a medical image of a lumen of a biological structure. The method facilitates vessel visualization in intravascular images (e.g. IVUS, OCT) used to evaluate the cardiovascular health of a patient. Using the methods and systems described herein it is simpler for a provider to evaluate vascular imaging data, which is typically distorted due to cardiac vessel-catheter motion while the image was acquired.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 14/044,990, filed Oct. 3, 2013, which claims priority to U.S.Provisional Application No. 61/710,410, filed Oct. 5, 2012. Thisapplication additionally claims priority to U.S. Provisional ApplicationNo. 61/781,660, filed Mar. 14, 2013. The contents of all of the notedapplications are incorporated by reference herein in their entireties.

FIELD OF THE INVENTION

The invention relates to methods and systems for correcting consecutiveimages of a lumen to compensate for motion of the lumen, motion of theimaging device, or variation of the placement of the imaging device withrespect to the center of the lumen.

BACKGROUND

Medical imaging is commonly used to evaluate various biologicalstructures of a patient. A common type of imaging system is a rotationalmedical imaging system (e.g., optical coherence tomography (OCT) orintravascular ultrasound (IVUS)). Those types of systems generallyacquire images of an inside of an anatomical structure having a lumen,for example a blood vessel or other similar vasculature.

Typically, such rotational systems include an imaging body that rotatesin a complete circle while being pulled back (or pushed forward) along apre-defined longitudinal length. The motion of the device as it acquiresimage data results in a series of two dimensional image frames, eachframe providing a 360° internal view of the vessel at a differentlocation as the device moves through the vessel. A series of thoseframes can be combined to construct a three-dimensional image of aninside of the vessel. Three dimensional images allow for easier and morefluid viewing of vasculature anatomy and afford a clinician an abilityto rapidly identify changes in a lumen border of the vasculature thatare attributable to a disease state (e.g., an embolism or extent ofarteriosclerosis).

Although rotational imaging systems have the potential for providingdetailed images of the inside of vessels, the displayed image oftenincludes various distortions arising during movement of the devicethrough the lumen. For example, distortions can include images in aseries appearing to be misaligned, improper display of vessel featuresdue to the imaging device not precisely following the contours of thevessel, or distortion arising from the helical motion of the device asit is moved through the vessel. These distortions result in considerableintra- and inter-observer variability that may lead to conflicting orincorrect patient diagnosis.

SUMMARY OF THE INVENTION

The invention provides methods and systems for correcting translationaldistortion in a medical image of a lumen of a biological structure. Thesystem assesses the position of the lumen with respect to one or morereference points for a first image and then determines the displacementof the first image from the reference point. The displacement of thefirst image is used to assess the displacements of the imagesimmediately preceding and immediately following the first image. Thedisplacement calculation is then performed iteratively for the entiredata set and the measured displacements are used to establish a commonreference, e.g., an average displacement. Once the common reference isestablished, each image is then transformed to compensate for thedisplacement with respect to the common reference, thus allowing acorrected image of the lumen to be created and displayed. A system ofthe invention includes a processor and memory upon which is storedinstructions to carry out the steps above. Some embodiments of thesystem additionally comprise an imaging device, e.g., an imagingcatheter.

The invention is generally applicable to data from any image gatheringdevices that acquire and process one, two, or three dimensional datasets from which three dimensional image compositions are derived.Exemplary devices include tomographic devices such as optical coherencetomography (OCT) devices, photo acoustic imaging devices, intravascularspectroscopy, intravascular magnetic resonance imaging, and ultrasounddevices, including intravascular ultrasound spectroscopy (IVUS). Theinvention is particularly well suited for imaging devices that make alarge number of measurements while rotating and translating, such aspull-back catheter imaging devices.

Through the use of the image processing techniques described herein, thevascular structure border for all imaging frames, or any subsetsthereof, in a recorded data set are corrected for image distortions andprovided to the user. Corrected lumen border images are provided to theuser in one, two and three dimensional image displays by the methods andsystems provided. The resulting corrected lumen border may be displayedas the final tomographic image, the image longitudinal display (ILD),splayed image and three dimensional image. User interface graphicsprovide input for other indicators on a monitor interface, such as acolor bar indicating the size of the lumen.

In other aspects, the invention embodies a system for displaying amedical image of a vessel. The system may use a monitor to display animage of the lumen of the biological structure, a central processingunit (CPU), and storage coupled to the CPU for storing instructions. Thesystem may be configured so that the CPU obtains image data of a lumenof a biological structure from an imaging device and corrects the imagedata for translational distortions and displays a corrected image.Alternatively, the image data may be collected with a device and storedfor later processing and use. In some embodiments, the system is used tocorrect images of intravascular lumen and the resulting images aredisplayed in a lumen-centric view.

The image data to be corrected may include any one of or combinations ofsplayed image data, image longitudinal display (ILD) data, threedimensional image data and tomographic image data. For example,tomographic image data that is acquired by an optical coherencetomography (OCT) catheter and corresponding OCT image data isparticularly suited for the methods and systems described. Exemplarytranslational distortions to be corrected include frame alignmentdistortion, device angular distortion, and helical offset distortion.

In one example, compensating for frame alignment distortion includesidentifying a reference position in each image frame and aligning eachframe using the reference position. Another example of compensating forframe alignment includes aligning the reference position in all framesand calculating a new reference position from the aligned frames. Aspecific reference position can be the center of the lumen, but anyreference position in the image frame can be used. Steps for aligning tothe center of a lumen may include fitting a geometric shape to a lumenborder, calculating a reference position within the area circumscribedby the geometric shape and aligning the image center to the referenceposition. The geometric shape to be fit to the lumen border includes,but is not limited to, a centroid, a circle or an ellipse. For greaterconsistency among frames for alignment purposes, the reference positioncan be smoothed across all image frames.

Another example includes compensating for angular distortionattributable to the imaging device. This example is generallyaccomplished as a multistep process. First, the method involves aligninga reference position of one frame with a catheter center position of aneighboring frame. Then, a longitudinal distance is determined betweenneighboring frames and an angle between two vectors is evaluated. Thefirst vector is defined by a distance between a reference position in afirst frame and a catheter center position in a neighboring frame, andthe second vector may be defined by a distance between a referenceposition in a first frame and a reference position in said neighboringframe. Next, the neighboring frame is rotated about an axis through avalue corresponding to the angle between the two vectors. The axis maybe located in a plane defined by the neighboring frame, intersecting thecatheter center position of the neighboring frame, and orientedperpendicular to a plane in which the first vector and second vector arelocated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a partial cross-sectional view of an imaging cathetersuitable for use with a rotational imaging system;

FIG. 2 illustrates a helical scanning pattern for a rotational imagingsystem;

FIG. 3 illustrates the geometry of a data stream acquired using thehelical scanning pattern of FIG. 2;

FIG. 4 illustrates an example of one source of distortion in OCT imagedata that is due to the change in position of a rotational imagingcatheter relative to a vessel lumen wall as it is longitudinallydisplaced within the length of a vessel;

FIG. 5 shows a single frame image of a vessel lumen appearing off-centerbecause the catheter occupies the center of the image;

FIG. 6 shows an image longitudinal display (ILD) composed of a series ofimage frames where the catheter position varies relative to the lumenborder. Each of the 200 individual lumen border images shifts out ofalignment from other image frame lumen borders through the series, whilethe catheter remains in alignment;

FIG. 7 shows an example of a splayed image two-dimensional map of avessel pullback;

FIG. 8 shows a three dimensional surface display of vessel lumen bordercentered relative to an imaging catheter. The three-dimensional displayis constructed from uncorrected two-dimensional images;

FIG. 9 is a flow chart illustrating an algorithm that may be used by asystem of the invention;

FIG. 10A illustrates the use of the algorithm of FIG. 9 to create avessel-centric image. In FIG. 10A the luminal images on the left arealigned with respect to the imaging axis, giving rise to an undulatinglongitudinal image on the right;

FIG. 10B illustrates an alternative use of the algorithm of FIG. 9 tocreate a vessel-centric image. In FIG. 10B the luminal images on theleft are aligned with respect to the vessel, giving rise to alongitudinal image with a substantially straight vessel but anundulating catheter image;

FIG. 11 illustrates an embodiment of the invention that maximizestile-to-tile similarities to establish transform conditions for the dataset;

FIG. 12A shows an exemplary IVUS pullback ILD image with acatheter-centric image;

FIG. 12B shows the IVUS pullback ILD image after transformation to avessel-centric image using a method of the invention. Variations in thevessel topology are much easier to identify in FIG. 12B, thereforeincreasing the likelihood of proper diagnosis;

FIG. 13 is a block diagram of an exemplary system for correctingtranslational distortion in a medical image of a lumen;

FIG. 14 is a block diagram of an exemplary system for correctingtranslational distortion in a medical image of a lumen;

FIG. 15 is a block diagram of an exemplary system for correctingtranslational distortion in a medical image of a lumen.

DETAILED DESCRIPTION

The invention provides methods and systems for correcting translationaldistortion in a medical image of a lumen of a biological structure. Themethod facilitates vessel visualization in intravascular images (e.g.IVUS, OCT) used to evaluate the cardiovascular health of a patient.Using the methods and systems described herein it is simpler for aprovider to evaluate vascular imaging data, which is typically distorteddue to cardiac vessel-catheter motion while the image was acquired. Theinvention applies a motion correction algorithm to the images prior togenerating vessel-centric images as an alternative to traditionalcatheter-centric display views.

Medical imaging is a general technology class in which sectional andmultidimensional anatomic images are constructed from acquired data. Thedata can be collected from a variety of acquisition systems including,but not limited to, magnetic resonance imaging (MRI), radiographymethods including fluoroscopy, x-ray tomography, computed axialtomography and computed tomography, optical coherence tomography (OCT),nuclear medicine techniques such as scintigraphy, positron emissiontomography and single photon emission computed tomography, photoacoustic imaging ultrasound devices and methods including, but notlimited to, intravascular ultrasound spectroscopy (IVUS), ultrasoundmodulated optical tomography, ultrasound transmission tomography, othertomographic techniques such as electrical capacitance, magneticinduction, functional MRI, optical projection and thermo-acousticimaging, combinations thereof and combinations with other medicaltechniques that produce two- and three-dimensional images. At least allof these techniques are contemplated for use with the systems andmethods of the present invention.

Medical imaging systems well suited for the present invention includerotational medical imaging systems. Exemplary rotational systems may useoptical coherence tomography (OCT), or may include other types ofimaging technology including, but not limited to, intravascularultrasound spectroscopy (IVUS), RAMAN spectroscopy, alternativeinterferometric techniques, therapeutic or diagnostic delivery devices,pressure wires, and the like. In the case of an optical imaging system,light sources can be laser light, tunable laser light, multiple tunablelaser lights with corresponding detectors, broadband light source,super-luminescent diode, tunable source, and the like.

Rotational system images (e.g. OCT and IVUS images) are acquired in thepolar domain with coordinates of radius and angle (r, theta) but need tobe converted to Cartesian coordinates (x, y) for display or rendering ona computer monitor. Typically, rotational systems consist of an imagingcore which rotates and pulls back (or pushes forward) while recording animage video loop. This motion results in a three dimensional dataset oftwo dimensional image frames, where each frame provides a 360° slice ofthe vessel at different longitudinal locations. Although theexemplifications described herein are drawn to the invention as appliedto OCT, the systems and methods are applicable to any imaging system,including at least those mentioned herein.

In some embodiments, the system can be used to correct images obtainedwith intravascular ultrasound imaging (IVUS). Accordingly, the imagingassembly can be a phased array IVUS imaging assembly, an pull-back typeIVUS imaging assembly, or an IVUS imaging assembly that usesphotoacoustic materials to produce diagnostic ultrasound and/or receivereflected ultrasound for diagnostics. IVUS imaging assemblies andprocessing of IVUS data are described for example in Yock, U.S. Pat.Nos. 4,794,931, 5,000,185, and 5,313,949; Sieben et al., U.S. Pat. Nos.5,243,988, and 5,353,798; Crowley et al., U.S. Pat. No. 4,951,677;Pomeranz, U.S. Pat. No. 5,095,911, Griffith et al., U.S. Pat. No.4,841,977, Maroney et al., U.S. Pat. No. 5,373,849, Born et al., U.S.Pat. No. 5,176,141, Lancee et al., U.S. Pat. No. 5,240,003, Lancee etal., U.S. Pat. No. 5,375,602, Gardineer et at., U.S. Pat. No. 5,373,845,Seward et al., Mayo Clinic Proceedings 71(7):629-635 (1996), Packer etal., Cardiostim Conference 833 (1994), “Ultrasound Cardioscopy,” Eur.J.C.P.E. 4(2):193 (June 1994), Eberle et al., U.S. Pat. No. 5,453,575,Eberle et al., U.S. Pat. No. 5,368,037, Eberle et at., U.S. Pat. No.5,183,048, Eberle et al., U.S. Pat. No. 5,167,233, Eberle et at., U.S.Pat. No. 4,917,097, Eberle et at., U.S. Pat. No. 5,135,486, and otherreferences well known in the art relating to intraluminal ultrasounddevices and modalities. All of these references are incorporated byreference herein.

Another medical imaging technique contemplated herein is opticalcoherence tomography (OCT). OCT systems and methods are generallydescribed in Milner et al., U.S. Patent Application Publication No.2011/0152771, Condit et al., U.S. Patent Application Publication No.2010/0220334, Castella et al., U.S. Patent Application Publication No.2009/0043191, Milner et al., U.S. Patent Application Publication No.2008/0291463, and Kemp, N., U.S. Patent Application Publication No.2008/0180683, the content of each of which is incorporated by referencein its entirety. OCT is a medical imaging methodology using a speciallydesigned catheter with a miniaturized near infrared light-emitting probeattached to the distal end of the catheter. As an optical signalacquisition and processing method, it captures micrometer-resolution,three-dimensional images from within optical scattering media (e.g.,biological tissue). OCT allows the application of interferometrictechnology to see from inside, for example, blood vessels, visualizingthe endothelium (inner wall) of blood vessels in living individuals. OCTsystems may be a spectrometer based OCT system or a Fourier Domain OCT,as disclosed in U.S. Patent Application No. 2009/0046295, hereinincorporated by reference.

Commercially available optical coherence tomography systems are employedin diverse applications, including art conservation and diagnosticmedicine, notably in ophthalmology where it can be used to obtaindetailed images from within the retina. Recently it has also begun to beused in interventional cardiology to help diagnose coronary arterydisease.

Various lumen of biological structures may be imaged with aforementionedimaging technologies in addition to blood vessels, including, but notlimited, to vasculature of the lymphatic and nervous systems, variousstructures of the gastrointestinal tract including lumen of the smallintestine, large intestine, stomach, esophagus, colon, pancreatic duct,bile duct, hepatic duct, lumen of the reproductive tract including thevas deferens, vagina, uterus and fallopian tubes, structures of theurinary tract including urinary collecting ducts, renal tubules, ureter,and bladder, and structures of the head and neck and pulmonary systemincluding sinuses, parotid, trachea, bronchi, and lungs.

The arteries of the heart are particularly useful to examine withimaging devices such as OCT. OCT imaging of the coronary arteries candetermine the amount of plaque built up at any particular point in thecoronary artery. The accumulation of plaque within the artery wall overdecades is the setup for vulnerable plaque which, in turn, leads toheart attack and stenosis (narrowing) of the artery. IVUS and OCT areuseful in determining both plaque volume within the wall of the artery,and the degree of stenosis of the artery lumen. It can be especiallyuseful in situations in which angiographic imaging is consideredunreliable, such as for the lumen of ostial lesions or whereangiographic images do not visualize lumen segments adequately. Exampleregions include those with multiple overlapping arterial segments. It isalso used to assess the effects of treatments of stenosis such as withhydraulic angioplasty expansion of the artery, with or without stents,and the results of medical therapy over time.

FIG. 1 illustrates an exemplary catheter 100 for rotational imaginginside a lumen of any anatomical or mechanical conduit, vessel, or tube.The exemplary catheter 100 is suitable for in vivo imaging, particularlyfor imaging of an anatomical lumen or passageway, such as acardiovascular, neurovascular, gastrointestinal, genitor-urinary tract,or other anatomical luminal structure. For example, FIG. 1 illustrates avascular lumen 102 within a vessel 104 including a plaque buildup 106.The exemplary catheter 100 may include a rapid access lumen 108 suitablefor guiding the catheter 100 over a guide-wire 110.

The exemplary catheter 100 is disposed over an exemplary rotationalimaging modality 112 that rotates about a longitudinal axis 114 thereofas indicated by arrow 116. The exemplary rotational imaging modality 112may comprise, in one embodiment, an OCT system. OCT is an opticalinterferometric technique for imaging subsurface tissue structure withmicrometer-scale resolution. In another embodiment, the exemplaryrotational imaging modality 112 may comprise an ultrasound imagingmodality, such as an IVUS system, either alone or in combination with anOCT imaging system. An exemplary OCT system may include a tunable laseror broadband light source or multiple tunable laser sources withcorresponding detectors, and may be a spectrometer based OCT system or aFourier Domain OCT system, as disclosed in U.S. Patent ApplicationPublication No. 2009/0046295, herein incorporated by reference. Theexemplary catheter 100 may be integrated with IVUS by an OCT-IVUS systemfor concurrent imaging, as described in, for example, Castella et al.U.S. Patent Application Publication No. 2009/0043191 and Dick et al.U.S. Patent Application Publication No. 2009/0018393, both incorporatedby reference in their entirety herein.

Referring to FIGS. 1 and 2, the rotational imaging modality 112 may belongitudinally translated during rotation, as indicated by line 118 inFIG. 1. Thus, the rotational imaging modality 112 acquires data along apath 120 that includes a combination of rotation and/or longitudinaltranslation of the rotational imaging modality 112. FIG. 2 illustratesan exemplary path 120, which is a helical scanning pattern 120,resulting from such a combination. Because FIG. 2 is a cross-sectionalview, the helical scanning pattern 120 is illustrated as would be tracedon a rear half of a luminal surface 122 of the scanned vessel 104. Thehelical scanning pattern 120 facilitates scanning a three-dimensionalspace within and beneath the luminal surface 122 longitudinally asdesired, but also introduces a data artifact commonly known as a seamline artifact during reconstruction of the data into a display frame, aswill be further discussed herein below.

Referring to FIGS. 1 and 2, the longitudinal axis 114 is illustrated aslinear for simplicity and clarity. However, the longitudinal axis 114 isnot necessarily linear as illustrated. The longitudinal axis 114 may becurvilinear having a curvature following a tortuosity of the vessel 104.It will be understood that vessel 104 need not be linear, but may infact have a curvilinear longitudinal axis 104 following the vessel 104along a tortuous geometry, and that the present invention equallyapplicable to an imaging modality 112 longitudinally translated alongthe vessel 104 having a longitudinally linear and/or tortuous geometry.

Referring to FIG. 3, a portion of the three dimensional space within andbeneath the luminal surface 122 scanned within a single rotationalperiod is projected into a planar (two-dimensional) format. In thisformat, line 126 represents a circumferential axis plotted horizontally.The geometry of a data stream acquired utilizing the above-describedhelical scan pattern 120 relative to the geometry of the luminal surface122 may be represented by the parallelogram 124 disposed over thehorizontal line 126 in FIG. 3. Starting at a fixed data acquisitionangle 200 (hereinafter a “FDAA 200”) conveniently denoted as zerodegrees (0°) in FIG. 3, the rotational imaging modality 112 acquiresdata following a rotational path indicated by line 128 (parallel to theline 126) in FIG. 3. However, because the rotational imaging modality112 may also be translated longitudinally, as indicated by line 130 inFIG. 3, the two-dimensional representation of the scannedthree-dimensional space within and beneath the luminal surface 122comprises the shape of the parallelogram 124. This means that at the endof one full rotation of the rotational imaging modality 112 as denotedin FIG. 3 by the FDAA 200 having a value of 360°, the rotational imagingmodality 112 has translated longitudinally by a distance Z.

To perform the analysis of a clinical condition, images acquired withthe rotational imaging devices are reconstructed in various displayformats. However, the displayed images often have artifacts generatedduring the acquisition or processing of the acquired data. Artifactsarise from, for example, shadows in the lumen border from stents andguide wires used in the catheter portion of the imaging device. Otherartifacts arise from any of a variety of dynamic motional effectsincluding, for example, cardiac motion of the patient or externalmovement of the catheter.

Because all scans are relative to the catheter imaging core, thecatheter is traditionally represented at the center of a tomographicimage. Accordingly, other artifacts include lumen image distortions andframe to frame offset or misalignment of the lumen due to the catheternot being centrally located during translational motion. Such distortionis typically ascribed to the inherent tortuosity of the biologicalstructure being imaged. Still other distortions arise from adiscontinuity of the imaging data for a two-dimensional image slice as aresult of the helical offset of the scan imaged. Such an offset arisesfrom the combined rotational and translational motions of the imagingdevice, in which during a full 360° rotational scan the imaging core hastranslated longitudinally be a distance Z.

Several image distortions commonly obtained from rotational imagingdevices are described in FIGS. 4-8. Catheters generally have lowductility relative to a lumen and cannot conform exactly to the tortuousshape of, for example, a blood vessel in which it is imaging. FIG. 4illustrates an example of one source of distortion in OCT image datathat is due to the change in position of a rotational imaging catheterrelative to a vessel lumen wall as it is longitudinally displaced withinthe length of a vessel. Because all images are relative to the catheterimaging core, the catheter always appears in the center of the image andsuccessive images appear as though the vessel is shifting positionaround the catheter imaging core. This effect will cause the vessel attimes to appear off-centered in the tomographic, splayed, two andthree-dimensional images and Image Longitudinal Displays (ILD). FIG. 5shows a single frame image of a vessel lumen appearing off-centerbecause the catheter occupies the center of the image. FIG. 6 shows anILD composed of a series of image frames where the catheter positionvaries relative to the lumen border. Each of the 200 individual lumenborder images shifts out of alignment from other image frame lumenborders through the series, while the catheter remains in alignment.Thus, in either the tomographic or ILD image frames obtained duringcatheter pullback, the vessel may appear to move around the catheter.

Another example of an image display type that often has a distortedpresentation is a “splayed image.” FIG. 7 shows an example of a splayedimage two-dimensional map of a vessel pullback. The x-axis is rotationalangle of the lumen border relative to the imaging device, and the y-axisis frame number. A splayed image is generated by integrating all pixelintensities beyond the vessel lumen border across all A-scans for allframes. Since a splayed image is constructed by integrating alongA-scans, the coordinates of the resulting signal are presented relativeto the catheter center, where the x-axis corresponds to the anglerelative to the center of the image. The stent struts, due to theirshadowing effect, are clearly seen in the image data. However, theangular spacing of the stent struts varies as caused by the eccentricityof the catheter during the pullback. The systems and methods describedherein can be used to correct distortions and create a more accuratedepiction of the stent distribution.

A three dimensional model of vessel wall is usually constructed throughthe acquisition of a series of two dimensional images, and thereforealso may display distortions based on those present in thetwo-dimensional images. FIG. 8 shows a three-dimensional surfacereconstruction of a vessel wall with distortional artifacts because itis constructed from uncorrected two-dimensional images. As in FIGS. 4-7,the position of the vessel wall is determined relative positioned to thecatheter, and therefore the surface of the three-dimensional model isslightly distorted by the change in position of the catheter along thepullback.

To counteract these distortions, systems of the invention determinecommon reference points in the acquired data and then transform the datato produce a vessel-centric image that is easier to analyze anddiagnose. In particular the invention uses a method in which (a)evaluates the geometric transformation sustained by a vessel betweenevery neighbor pair of acquired images, then (b) filters thetransformations accumulated during image acquisition, (c) computes thespecific motion compensation to transform the images in order to get thevessel spatially stabilized, and finally (d) applies the transformationsto the tomographic images and reconstructs longitudinal views of thevessel for display.

The primary advantage is the ability to create vessel-centric displayviews consistently stabilizing vessel position and orientation along apullback. The known methods suffer from their inability to achievevessel alignment for more than a few image frames, inability tocompensate for significant vessel shift, and/or inability to hold thecatheter within a longitudinal field of view. The secondary advantage isthat longitudinal views are still directly generated from the acquiredimaging scan lines, unlike other methods which include additionalcompensation-related scan conversions that cause interpolationartifacts.

The resultant vessel-centric views provide users with a clearer and moreconsistent visual appearance of the vessel anatomy than traditionalcatheter-centric views. Moreover, the vessel-centric image availabilityfacilitates further automated analysis of the anatomy, for example,segmentation of lumen and adventitia, plaque characterization, andlikewise. The method can be used in any intravascular proceduresinvolving an imaging catheter in a coronary artery where physiologiccardiac motion occurs. It can be used in diagnostic and/or image-guidedtherapy purposes. It can be applied to different imaging modalities suchas IVUS, OCT, intravascular spectroscopy, photo-acoustic tomography andsimilar. The method is not restricted to planar scanning in an imagingplane orthogonal to the vessel axis, and it is also applicable withconical scanning geometry such as used in forward-looking IVUS imaging.

As described in FIG. 9, the method principally involves evaluating eachimage data set for vessel markers, and compiling the positions of thevessel markers to establish a transform function that is used toindividually reverse transform each frame so that the corrected framescan be assembled into one or more images, e.g., tomographic views. Asshown in FIGS. 10A and 10B, the imaging data may be acquired from anintravascular catheter in polar form, i.e., comprising a sequence ofimage frames consisting of radial scan lines. Alternatively, the imageframes can be scan converted from polar to Cartesian prior totransformation.

In order to describe catheter-vessel motion quantitatively, the accruedvessel movements are detected using image registration methods such asrigid or non-rigid spatial transformations between each neighbor imageframe pairs. For example, as shown in FIG. 11, the acquired polar imagescan be broken into a number of small tiles, local correlations arecalculated for spatially shuffled tiles across frames, the local maximacorresponding to local radial and lateral translations are identified,and finally an integral rigid transformation best matching to thepattern of local translations is determined for the image as a whole inCartesian space. The detected rigid transformations between eachneighbor image frame pairs are continuously accumulated over a pullback.The accumulated transformation represents an integral spatial relationbetween the current frame and the first frames in a pullback.

While there is a potential for accumulation of stray errors for longframe sequences, such errors can be addressed by filtering the sequenceof accumulated transformations. For example, a temporal filter may beapplied to compensate for a DC offset and to smooth out any jittercaused by errors in detection of elementary transformations betweenneighboring frame pairs. In another instance the filtering step canemploy two separate bandpass filters, one for the rotational and one forthe translational components of the accumulated rigid transformation.Each of those filters can, for example, consist of a weighted average ofthe three most recent accumulated values to smooth out any jitter thatis followed by a subtraction of a “longer term” averaged over sixtyrecent frames value to compensate for a DC offset. Once the filteredaccumulated transformation for an image frame is obtained, motioncompensation is computed to spatially align the vessel across the framesequence. The computed compensation aims to present the vessel anatomyin the images as if there were no cardiac motion

Once the transformation function has been identified, each tomographicframe is reverse transformed to normalize the entire image set. Based ona frame sequence and the corresponding sequence of compensationtransformations, a series of stabilized tomographic frames can beproduced, where the vessel appears stationary and the catheter appearsto float within the vessel. As a result of compensating for the DCoffset, the catheter floating is bounded by short-term cardiac motionwithin the few nearest cardiac cycles in the pullback and any drasticdrift out of the field of view is prevented.

The application of the algorithm of the invention to an IVUS vascularimage is shown in FIGS. 12A and 12B. The ILD view represents alongitudinal cross-section through a sequence of frames created byselecting two diametrically opposed scan lines from each frame andstacking them into an image. In FIG. 12A, the sequence of frames isassembled using the imaging axis as a reference point, which is standardmethod in many imaging systems. However, in FIG. 12B, the scan lines areassembled as a series of motion compensated frames. The filteredaccumulated rigid transformation is decomposed into its rotational andtranslational components, and the rotational component is subtractedfrom the ILD view cross-sectional angle to determine the motioncompensated diameter. Next, the selected scan lines are shifted radiallywithin the ILD and the applied radial shift equals to the projection ofthe negative of the translational component discussed above. This radialshift allows the catheter center to float within the ILD view accordingto the detected motion. At the same time any transversal motion of thecatheter center gets absorbed by the ILD view so that the entire motioncompensated diameter remains visible, similarly to a curved multi-planarreconstruction commonly used in radiography.

In some embodiments, the composed ILD view is further placed into aviewport, for example cropped to a rectangular window and rendered in adisplay. Based on a frame sequence and a respective sequence ofcompensation transformations, any number of ILD views corresponding to anumber of cross-sections with different view angles can be generated inparallel in order to let users interactively control the view anglebeing rendered.

A system of the invention may be implemented in a number of formats. Anembodiment of a system 300 of the invention is shown in FIG. 13. Thecore of the system 300 is a computer 360 or other computationalarrangement comprising a processor 365 and memory 367. The memory hasinstructions which when executed cause the processor to determine abaseline measurement prior to conducting a therapeutic procedure anddetermine a post-therapy measurement after conducting the therapeuticprocedure. The instructions may also cause the computer to compare thepost-therapy measurement to the baseline measurement, therebydetermining the degree of post-therapy improvement after conducting thetherapeutic procedure. The physiological measurement data of vasculaturewill typically originate from an intravascular measurement device 320,which is in electronic and/or mechanical communication with a sensingcatheter 325. Having collected the baseline measurement and post-therapymeasurement, the processor then processes and outputs the results. Theresults are typically output to a display 380 to be viewed by aphysician or technician.

In advanced embodiments, system 300 may comprise an imaging engine 370which has advanced image processing features, such as image tagging,that allow the system 300 to more efficiently process and displayintravascular and angiographic images. The imaging engine 370 mayautomatically highlight or otherwise denote areas of interest in thevasculature. The imaging engine 370 may also produce 3D renderings orother visual representations of the physiological measurements. In someembodiments, the imaging engine 370 may additionally include dataacquisition functionalities (DAQ) 375, which allow the imaging engine370 to receive the physiological measurement data directly from thecatheter 325 or collector 347 to be processed into images for display.

Other advanced embodiments use the I/O functionalities 362 of computer360 to control the intravascular measurement 320. In these embodiments,computer 360 may cause the imaging assembly of catheter 325 to travel toa specific location, e.g., if the catheter 325 is a pull-back type.While not shown here, it is also possible that computer 360 may controla manipulator, e.g., a robotic manipulator, connected to catheter 325 toimprove the placement of the catheter 325.

A system 400 of the invention may also be implemented across a number ofindependent platforms which communicate via a network 409, as shown inFIG. 14. Methods of the invention can be performed using software,hardware, firmware, hardwiring, or combinations of any of these.Features implementing functions can also be physically located atvarious positions, including being distributed such that portions offunctions are implemented at different physical locations (e.g., imagingapparatus in one room and host workstation in another, or in separatebuildings, for example, with wireless or wired connections).

As shown in FIG. 14, the intravascular detecting system 320 facilitateobtaining the data, however the actual implementation of the steps canbe performed by multiple processors working in communication via thenetwork 409, for example a local area network, a wireless network, orthe internet. The components of system 400 may also be physicallyseparated. For example, terminal 467 and display 380 may not begeographically located with the intravascular detection system 320.

As shown in FIG. 14, imaging engine 859 communicates with hostworkstation 433 as well as optionally server 413 over network 409. Insome embodiments, an operator uses host workstation 433, computer 449,or terminal 467 to control system 400 or to receive images. An image maybe displayed using an I/O 454, 437, or 471, which may include a monitor.Any I/O may include a monitor, keyboard, mouse, or touch screen tocommunicate with any of processor 421, 459, 441, or 475, for example, tocause data to be stored in any tangible, nontransitory memory 463, 445,479, or 429. Server 413 generally includes an interface module 425 tocommunicate over network 409 or write data to data file 417. Input froma user is received by a processor in an electronic device such as, forexample, host workstation 433, server 413, or computer 449. In certainembodiments, host workstation 433 and imaging engine 855 are included ina bedside console unit to operate system 400.

In some embodiments, the system may render three dimensional imaging ofthe vasculature or the intravascular images. An electronic apparatuswithin the system (e.g., PC, dedicated hardware, or firmware) such asthe host workstation 433 stores the three dimensional image in atangible, non-transitory memory and renders an image of the 3D tissueson the display 380. In some embodiments, the 3D images will be coded forfaster viewing. In certain embodiments, systems of the invention rendera GUI with elements or controls to allow an operator to interact withthree dimensional data set as a three dimensional view. For example, anoperator may cause a video affect to be viewed in, for example, atomographic view, creating a visual effect of travelling through a lumenof vessel (i.e., a dynamic progress view). In other embodiments anoperator may select points from within one of the images or the threedimensional data set by choosing start and stop points while a dynamicprogress view is displayed in display. In other embodiments, a user maycause an imaging catheter to be relocated to a new position in the bodyby interacting with the image.

In some embodiments, a user interacts with a visual interface and putsin parameters or makes a selection. Input from a user (e.g., parametersor a selection) are received by a processor in an electronic device suchas, for example, host workstation 433, server 413, or computer 449. Theselection can be rendered into a visible display. In some embodiments,an operator uses host workstation 433, computer 449, or terminal 467 tocontrol system 400 or to receive images. An image may be displayed usingan I/O 454, 437, or 471, which may include a monitor. Any I/O mayinclude a keyboard, mouse or touch screen to communicate with any ofprocessor 421, 459, 441, or 475, for example, to cause data to be storedin any tangible, nontransitory memory 463, 445, 479, or 429. Server 413generally includes an interface module 425 to effectuate communicationover network 409 or write data to data file 417. Methods of theinvention can be performed using software, hardware, firmware,hardwiring, or combinations of any of these. Features implementingfunctions can also be physically located at various positions, includingbeing distributed such that portions of functions are implemented atdifferent physical locations (e.g., imaging apparatus in one room andhost workstation in another, or in separate buildings, for example, withwireless or wired connections). In certain embodiments, host workstation433 and imaging engine 855 are included in a bedside console unit tooperate system 400.

Processors suitable for the execution of computer program include, byway of example, both general and special purpose microprocessors, andany one or more processor of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only memory ora random access memory or both. The essential elements of computer are aprocessor for executing instructions and one or more memory devices forstoring instructions and data. Generally, a computer will also include,or be operatively coupled to receive data from or transfer data to, orboth, one or more mass storage devices for storing data, e.g., magnetic,magneto-optical disks, or optical disks. Information carriers suitablefor embodying computer program instructions and data include all formsof non-volatile memory, including by way of example semiconductor memorydevices, (e.g., EPROM, EEPROM, NAND-based flash memory, solid statedrive (SSD), and other flash memory devices); magnetic disks, (e.g.,internal hard disks or removable disks); magneto-optical disks; andoptical disks (e.g., CD and DVD disks). The processor and the memory canbe supplemented by, or incorporated in, special purpose logic circuitry.

To provide for interaction with a user, the subject matter describedherein can be implemented on a computer having an I/O device, e.g., aCRT, LCD, LED, or projection device for displaying information to theuser and an input or output device such as a keyboard and a pointingdevice, (e.g., a mouse or a trackball), by which the user can provideinput to the computer. Other kinds of devices can be used to provide forinteraction with a user as well. For example, feedback provided to theuser can be any form of sensory feedback, (e.g., visual feedback,auditory feedback, or tactile feedback), and input from the user can bereceived in any form, including acoustic, speech, or tactile input.

The subject matter described herein can be implemented in a computingsystem that includes a back-end component (e.g., a data server 413), amiddleware component (e.g., an application server), or a front-endcomponent (e.g., a client computer 449 having a graphical user interface454 or a web browser through which a user can interact with animplementation of the subject matter described herein), or anycombination of such back-end, middleware, and front-end components. Thecomponents of the system can be interconnected through network 409 byany form or medium of digital data communication, e.g., a communicationnetwork. Examples of communication networks include cell networks (3G,4G), a local area network (LAN), and a wide area network (WAN), e.g.,the Internet.

The subject matter described herein can be implemented as one or morecomputer program products, such as one or more computer programstangibly embodied in an information carrier (e.g., in a non-transitorycomputer-readable medium) for execution by, or to control the operationof, data processing apparatus (e.g., a programmable processor, acomputer, or multiple computers). A computer program (also known as aprogram, software, software application, app, macro, or code) can bewritten in any form of programming language, including compiled orinterpreted languages (e.g., C, C++, Perl), and it can be deployed inany form, including as a stand-alone program or as a module, component,subroutine, or other unit suitable for use in a computing environment.Systems and methods of the invention can include programming languageknown in the art, including, without limitation, C, C++, Perl, Java,ActiveX, HTML5, Visual Basic, or JavaScript.

A computer program does not necessarily correspond to a file. A programcan be stored in a portion of file 417 that holds other programs ordata, in a single file dedicated to the program in question, or inmultiple coordinated files (e.g., files that store one or more modules,sub-programs, or portions of code). A computer program can be deployedto be executed on one computer or on multiple computers at one site ordistributed across multiple sites and interconnected by a communicationnetwork.

A file can be a digital file, for example, stored on a hard drive, SSD,CD, or other tangible, non-transitory medium. A file can be sent fromone device to another over network 409 (e.g., as packets being sent froma server to a client, for example, through a Network Interface Card,modem, wireless card, or similar).

Writing a file according to the invention involves transforming atangible, non-transitory computer-readable medium, for example, byadding, removing, or rearranging particles (e.g., with a net charge ordipole moment) into patterns of magnetization by read/write heads, thepatterns then representing new collocations of information desired by,and useful to, the user. In some embodiments, writing involves aphysical transformation of material in tangible, non-transitory computerreadable media with certain properties so that optical read/writedevices can then read the new and useful collocation of information(e.g., burning a CD-ROM). In some embodiments, writing a file includesusing flash memory such as NAND flash memory and storing information inan array of memory cells include floating-gate transistors. Methods ofwriting a file are well-known in the art and, for example, can beinvoked automatically by a program or by a save command from software ora write command from a programming language.

In certain embodiments, display 380 is rendered within a computeroperating system environment, such as Windows, Mac OS, or Linux orwithin a display or GUI of a specialized system. Display 380 can includeany standard controls associated with a display (e.g., within awindowing environment) including minimize and close buttons, scrollbars, menus, and window resizing controls. Elements of display 380 canbe provided by an operating system, windows environment, applicationprogramming interface (API), web browser, program, or combinationthereof (for example, in some embodiments a computer includes anoperating system in which an independent program such as a web browserruns and the independent program supplies one or more of an API torender elements of a GUI). Display 380 can further include any controlsor information related to viewing images (e.g., zoom, color controls,brightness/contrast) or handling files comprising three-dimensionalimage data (e.g., open, save, close, select, cut, delete, etc.).Further, display 380 can include controls (e.g., buttons, sliders, tabs,switches) related to operating a three dimensional image capture system(e.g., go, stop, pause, power up, power down).

In certain embodiments, display 380 includes controls related to threedimensional imaging systems that are operable with different imagingmodalities. For example, display 380 may include start, stop, zoom,save, etc., buttons, and be rendered by a computer program thatinteroperates with IVUS, OCT, or angiogram modalities. Thus display 380can display an image derived from a three-dimensional data set with orwithout regard to the imaging mode of the system.

Alternatively, an imaging data set may be assessed, analyzed, andtransformed with a system such as the system shown in FIG. 15,comprising CPU 1510, storage 1520, and monitor 1530. Storage 1520 maycontain instructions for carrying out methods of the invention, e.g., toconfigure CPU 1510 to analyze the imaging data set for a parameter,assign an indicator to the medical device based on the presence of theparameter, and display the indicator on monitor 1530. For example CPU1510 may direct monitor 1530 to display a longitudinal image of a lumenwith a color-coded stent. In some embodiments, a system of the inventionwill additionally comprise graphical user interface (GUI) 1540, whichallows a user to interact with the images. In some embodiments, CPU1510, storage 1520, and monitor 1530 may be encompassed within system2400.

The systems and methods of use described herein can be performed usingany type of computing device, such as a computer, that includes aprocessor or any combination of computing devices where each deviceperforms at least part of the process or method. In some embodiments,systems and methods described herein may be performed with a handhelddevice, e.g., a smart tablet, or a smart phone, or a specialty deviceproduced for the system.

In some embodiments, a device of the invention includes an OCT imagingsystem and obtains a three-dimensional data set through the operation ofOCT imaging hardware. In some embodiments, a device of the invention isa computer device such as a laptop, desktop, or tablet computer, andobtains a three-dimensional data set by retrieving it from a tangiblestorage medium, such as a disk drive on a server using a network or asan email attachment.

Methods of the invention can be performed using software, hardware,firmware, hardwiring, or combinations of any of these. Featuresimplementing functions can also be physically located at variouspositions, including being distributed such that portions of functionsare implemented at different physical locations (e.g., imaging apparatusin one room and host workstation in another, or in separate buildings,for example, with wireless or wired connections).

Any target can be imaged by methods and systems of the inventionincluding, for example, bodily tissue. In certain embodiments, systemsand methods of the invention image within a lumen of tissue. Variouslumen of biological structures may be imaged including, but not limitedto, blood vessels, vasculature of the lymphatic and nervous systems,various structures of the gastrointestinal tract including lumen of thesmall intestine, large intestine, stomach, esophagus, colon, pancreaticduct, bile duct, hepatic duct, lumen of the reproductive tract includingthe vas deferens, vagina, uterus and fallopian tubes, structures of theurinary tract including urinary collecting ducts, renal tubules, ureter,and bladder, and structures of the head and neck and pulmonary systemincluding sinuses, parotid, trachea, bronchi, and lungs.

Incorporation by Reference

References and citations to other documents, such as patents, patentapplications, patent publications, journals, books, papers, webcontents, have been made throughout this disclosure. All such documentsare hereby incorporated herein by reference in their entirety for allpurposes.

Equivalents

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The foregoingembodiments are therefore to be considered in all respects illustrativerather than limiting on the invention described herein. Scope of theinvention is thus indicated by the appended claims rather than by theforegoing description, and all changes which come within the meaning andrange of equivalency of the claims are therefore intended to be embracedtherein.

The invention claimed is:
 1. A system for transforming an image of a lumen, comprising: a processor; and storage coupled to the processor, the storage comprising instructions that when executed cause the processor to: receive data corresponding to a first image of a lumen; register coordinates of at least two points in the first image of the lumen; receive data corresponding to a second image of a lumen; register coordinates of at least two points in the second image of the lumen; receive data corresponding to a third image of a lumen; register coordinates of at least two points in the third image of the lumen; compare the coordinates of the at least two points in the first image of the lumen to the at least two points in the second image of the lumen and to the coordinates of the at least two points in the third image of the lumen; determine a translation to align the at least two points in the first image of the lumen, the at least two points in the second image of the lumen, and the at least two points in the third image of the lumen; translate the first image to align the at least two points in the first image of the lumen, the at least two points in the second image of the lumen, and the at least two points in the third image of the lumen; and output data corresponding to an image comprising the first, second, and third images of the lumen.
 2. The system of claim 1, wherein the data corresponding to the images of the lumen is acquired with optical coherence tomography (OCT).
 3. The system of claim 1, wherein the data corresponding to the images of the lumen is acquired with intravenous ultrasound imaging (IVUS).
 4. The system of claim 1, wherein the translated image corrects for frame alignment distortion, device angular distortion, device translational distortion, helical offset distortion, cardiac motion distortions, or combination thereof.
 5. The system of claim 4, wherein the translated image corrects for frame alignment distortions.
 6. The system of claim 1, wherein the storage additionally comprises instructions that cause the processor to smooth the data corresponding to an image comprising the first, second, and third images of the lumen.
 7. The system of claim 1, wherein image comprising the first, second, and third images is selected from a splayed image, an image longitudinal display (ILD) image, a three dimensional image, a tomographic image, or a combination thereof.
 8. The system of claim 1, wherein the lumen is a vessel.
 9. The system of claim 1, wherein the third, first, and second images are taken consecutively in time.
 10. The system of claim 1, wherein the at least two points in the first image are points on a lumen border.
 11. A method comprising providing at least one computer-readable medium having instructions stored thereon which, when executed by a computing device, cause the computing device to carry out operations comprising: receiving data corresponding to a first image of a lumen; registering coordinates of at least two points in the first image of the lumen; receiving data corresponding to a second image of a lumen; registering coordinates of at least two points in the second image of the lumen; receiving data corresponding to a third image of a lumen; registering coordinates of at least two points in the third image of the lumen; comparing the coordinates of the at least two points in the first image of the lumen to the coordinates of the at least two points in the second image of the lumen and to the coordinates of the at least two points in the third image of the lumen; determining a translation to align the at least two points in the first image of the lumen, the at least two points in the second image of the lumen, and the at least two points in the third image of the lumen; translating the first image to align the at least two points in the first image of the lumen, the at least two points in the second image of the lumen, and the at least two points in the third image of the lumen; and outputting data corresponding to an image comprising the first, second and third images of the lumen.
 12. The method of claim 11, further comprising smoothing the data corresponding to an image comprising the first, second, and third images of the lumen.
 13. A system for transforming an image of a lumen, comprising: a processor; and storage coupled to the processor, the storage comprising instructions that when executed cause the processor to: receive data corresponding to a first image of a lumen; register coordinates of at least two points in the first image of the lumen; receive data corresponding to a second image of a lumen; register coordinates of at least two points in the second image of the lumen; receive data corresponding to a third image of a lumen; register coordinates of at least two points in the third image of the lumen; compare the coordinates of the at least two points in the first image of the lumen to the at least two points in the second image of the lumen and to the coordinates of the at least two points in the third image of the lumen; determine a translation to align the at least two points in the first image of the lumen, the at least two points in the second image of the lumen, and the at least two points in the third image of the lumen; translate the first image to align the at least two points in the first image of the lumen, the at least two points in the second image of the lumen, and the at least two points in the third image of the lumen; and wherein the third, first, and second images are taken consecutively in time. 